The present invention relates to a method of producing a refractory brick, and is especially applicable to the production of light-weight refractory bricks.
Refractory light-weight bricks that are made from a watery slurry are known. The slurry contains a refractory granular material such as, for example, fired clay and sintered alumina having a grain size up to 2 mm, a binder, and a pore-forming foaming agent. The binder may consist of a solution of sulphite spent liquor (sodium lignosulphonate), methylcellulose, sodium silicate, a sodiumphosphate compound, a sol of silicic acid, or an aqueous binder.
According to West German Unexamined Application No. 1 965 008, a watery colloidal dispersion of silicon oxide or aluminum oxide is used for the manufacture of a ceramic light-weight product. During heating of the mixture in molds, foam is generated by decomposing alkali carbonate, and the molding is allowed to set. According to U.S. Pat. No. 2,235,881, a porous fired brick is produced from a ceramic slurry containing a foaming agent. To achieve stiffening by the formation of an aluminum oxide gel, an aluminum salt, such as aluminum chloride, is first added to the mixture, then, as the last component of the mixture, ammonium hydroxide is added.
The manufacture of these refractory light-weight bricks involves complex production steps and the formation of gases that are hazardous to health. Furthermore, the bricks obtained after the stiffening and setting of the mixtures do not have satisfactory properties and, in particular, they lack sufficient strength.
Aluminumhydroxychloride (Al.sub.2 (OH).sub.5 Cl.2-3H.sub.2 O) can also be employed as a binder for refractory products with a high bulk density, and is stable in an acidic aqueous solution under a pH value of 5. Bonding and setting occur with the thermal treatment of the moldings by drying and firing.